1. Field of the Invention
The invention generally relates to the field of immunology and immunotherapy, and more specifically to immune regulatory oligonucleotide (IRO) compositions and their use for inhibition and/or suppression of Toll-like Receptor-mediated immune responses.
2. Summary of the Related Art
Toll-like receptors (TLRs) are present on many cells of the immune system and have been shown to be involved in the innate immune response (Hornung, V. et al., (2002) J. Immunol. 168:4531-4537). In vertebrates, this family consists of ten proteins called TLR1 to TLR10, which are known to recognize pathogen associated molecular patterns from bacteria, fungi, parasites, and viruses (Poltorak, a. et al. (1998) Science 282:2085-2088; Underhill, D. M., et al. (1999) Nature 401:811-815; Hayashi, F. et. al (2001) Nature 410:1099-1103; Zhang, D. et al. (2004) Science 303:1522-1526; Meier, A. et al. (2003) Cell. Microbiol. 5:561-570; Campos, M. A. et al. (2001) J. Immunol. 167: 416-423; Hoebe, K. et al. (2003) Nature 424: 743-748; Lund, J. (2003) J. Exp. Med. 198:513-520; Heil, F. et al. (2004) Science 303:1526-1529; Diebold, S. S., et al. (2004) Science 303:1529-1531; Hornung, V. et al. (2004) J. Immunol. 173:5935-5943). TLRs are a key means by which mammals recognize and mount an immune response to foreign molecules and also provide a means by which the innate and adaptive immune responses are linked (Akira, S. et al. (2001) Nature Immunol. 2:675-680; Medzhitov, R. (2001) Nature Rev. Immunol. 1:135-145). TLRs have also been shown to play a role in the pathogenesis of many diseases, including autoimmunity, infectious disease, and inflammation (Cook, D. N. et al. (2004) Nature Immunol. 5:975-979) and the regulation of TLR-mediated activation using appropriate agents may provide a means for disease intervention.
Some TLRs are located on the cell surface to detect and initiate a response to extracellular pathogens and other TLRs are located inside the cell to detect and initiate a response to intracellular pathogens. Table 1 provides a representation of TLRs and the known agonists therefore (Diebold, S. S. et al. (2004) Science 303:1529-1531; Liew, F. et al. (2005) Nature 5:446-458; Hemmi H et al. (2002) Nat Immunol 3:196-200; Jurk M et al., (2002) Nat Immunol 3:499; Lee J et al. (2003) Proc. Natl. Acad. Sci. USA 100:6646-6651); (Alexopoulou, L. (2001) Nature 413:732-738).
TABLE 1TLR MoleculeAgonistCell Surface TLRs:TLR2bacterial lipopeptidesTLR4gram negative bacteriaTLR5motile bacteriaTLR6gram positive bacteriaEndosomal TLRs:TLR3double stranded RNA virusesTLR7single stranded RNA virusesTLR8single stranded RNA virusesTLR9unmethylated DNA
Certain unmethylated CpG motifs present in bacterial and synthetic DNA have been shown to activate the immune system and induce antitumor activity. (Tokunaga T et al., J. Natl. Cancer Inst. (1984) 72:955-962; Shimada S, et al., Jpn. H cancer Res, 1986, 77, 808-816; Yamamoto S, et al., Jpn. J. Cancer Res., 1986, 79, 866-73). Other studies using antisense oligonucleotides containing CpG dinucleotides have been shown to stimulate immune responses (Zhao Q, et al. (1996) Biochem. Pharmacol. 26:173-182). Subsequent studies demonstrated that TLR9 recognizes unmethylated CpG motifs present in bacterial and synthetic DNA (Hemmi, H. et al. (2000) Nature 408:740-745). Other modifications of CpG-containing phosphorothioate oligonucleotides can also affect their ability to act as modulators of immune response through TLR9 (see, e.g., Zhao et al., Biochem. Pharmacol. (1996) 51:173-182; Zhao et al. (1996) Biochem Pharmacol. 52:1537-1544; Zhao et al. (1997) Antisense Nucleic Acid Drug Dev. 7:495-502; Zhao et al (1999) Bioorg. Med. Chem. Lett. 9:3453-3458; Zhao et al. (2000) Bioorg. Med. Chem. Lett. 10:1051-1054; Yu, D. et al. (2000) Bioorg. Med. Chem. Lett. 10:2585-2588; Yu, D. et al. (2001) Bioorg. Med. Chem. Lett. 11:2263-2267; and Kandimalla, E. et al. (2001) Bioorg. Med. Chem. 9:807-813). In addition, structure activity relationship studies have allowed identification of synthetic motifs and novel DNA-based compounds that induce specific immune response profiles that are distinct from those resulting from unmethylated CpG dinucleotides. (Kandimalla, E. et al. (2005) Proc. Natl. Acad. Sci. USA 102:6925-6930. Kandimalla, E. et al. (2003) Proc. Nat. Acad. Sci. USA 100:14303-14308; Cong, Y. et al. (2003) Biochem Biophys Res. Commun. 310:1133-1139; Kandimalla, E. et al. (2003) Biochem. Biophys. Res. Commun. 306:948-953; Kandimalla, E. et al. (2003) Nucleic Acids Res. 31:2393-2400; Yu, D. et al. (2003) Bioorg. Med. Chem. 11:459-464; Bhagat, L. et al. (2003) Biochem. Biophys. Res. Commun. 300:853-861; Yu, D. et al. (2002) Nucleic Acids Res. 30:4460-4469; Yu, D. et al. (2002) J. Med. Chem. 45:4540-4548. Yu, D. et al. (2002) Biochem. Biophys. Res. Commun. 297:83-90; Kandimalla. E. et al. (2002) Bioconjug. Chem. 13:966-974; Yu, D. et al. (2002) Nucleic Acids Res. 30:1613-1619; Yu, D. et al. (2001) Bioorg. Med. Chem. 9:2803-2808; Yu, D. et al. (2001) Bioorg. Med. Chem. Lett. 11:2263-2267; Kandimalla, E. et al. (2001) Bioorg. Med. Chem. 9:807-813; Yu, D. et al. (2000) Bioorg. Med. Chem. Lett. 10:2585-2588; Putta, M. et al. (2006) Nucleic Acids Res. 34:3231-3238).
The selective localization of TLRs and the signaling generated therefrom, provides some insight into their role in the immune response. The immune response involves both an innate and an adaptive response based upon the subset of cells involved in the response. For example, the T helper (Th) cells involved in classical cell-mediated functions such as delayed-type hypersensitivity and activation of cytotoxic T lymphocytes (CTLs) are Th1 cells. This response is the body's innate response to antigen (e.g. viral infections, intracellular pathogens, and tumor cells), and results in a secretion of IFN-gamma and a concomitant activation of CTLs. Alternatively, the Th cells involved as helper cells for B-cell activation are Th2 cells. Th2 cells have been shown to be activated in response to bacteria and parasites and may mediate the body's adaptive immune response (e.g. IgE production and eosinophil activation) through the secretion of IL-4 and IL-5. The type of immune response is influenced by the cytokines produced in response to antigen exposure and the differences in the cytokines secreted by Th1 and Th2 cells may be the result of the different biological functions of these two subsets.
While activation of TLRs is involved in mounting an immune response, an uncontrolled stimulation of the immune system through TLRs may exacerbate certain diseases in immune compromised subjects. In recent years, several groups have shown the use of synthetic oligodeoxyoligonucleotides (ODNs) as inhibitors of inflammatory cytokines (Lenert, P. et al. (2003) DNA Cell Biol. 22 (10):621-631).
Using certain synthetic ODNs, Lenert et al. report the ability to produce inhibitory ODNs (Lenert, P. et al. (2003) DNA Cell Biol. 22 (10):621-631). These inhibitory ODN require two triplet sequences, a proximal “CCT” triplet and a distal “GGG” triplet. In addition to these triplet-containing inhibitory ODNs, several groups have reported other specific DNA sequences that could inhibit TLR-9-mediated activation by CpG-containing ODNs. These “inhibitory” or “suppressive” motifs are rich in poly “G” (e.g. “GGGG”) or “GC” sequences, tend to be methylated, and are present in the DNA of mammals and certain viruses (see e.g., Chen, Y., et al., Gene Ther. 8: 1024-1032 (2001); Stunz, L. L., Eur. J. Immunol. 32: 1212-1222 (2002). Duramad, O., et al., J. Immunol., 174: 5193-5200 (2005) and Jurk et. al (US 2005/0239733), describe a structure for inhibitory DNA oligonucleotides containing a GGGG motif within the sequences. Patole et al. demonstrate that GGGG containing ODNs will suppress systemic lupus (Patole, P. et al. (2005) J. Am. Soc. Nephrol. 16:3273-3280). Additionally, Gursel, I., et al., J. Immunol., 171: 1393-1400 (2003), describe repetitive TTAGGG elements, which are present at high frequency in mammalian telomeres, down-regulate CpG-induced immune activation. Shirota, H., et al., J. Immunol., 173: 5002-5007 (2004), demonstrate that synthetic oligonucleotides containing the TTAGGG element mimic this activity and could be effective in the prevention/treatment of certain Th1-dependent autoimmune diseases.
In contrast, recent studies have called into question the view that poly G containing ODNs are acting as antagonists of TLRs. For example, U.S. Pat. No. 6,426,334, Agrawal et al., demonstrate that administering CpG oligonucleotides containing GGGG strings have potent antiviral and anticancer activity, and further that administration of these compounds will cause an increase in serum IL-12 concentration. Further, CpG oligos containing polyG sequences are known to induce immune responses through TLR9 activation (Verthelyi D et al, J. Immunol. 166, 2372, 2001; Gursel M et al, J Leukoc Biol, 71, 813, 2001, Krug A et al, Eur J Immunol, 31, 2154, 2001) and show antitumor, antiviral activities (Ballas G K et al, J Immunol, 167, 4878, 2001; Verthelyi D et al, J Immunol, 170, 4717, 2003). In addition, polyG oligonucleotides are also known to inhibit HIV and Rel A (McShan W M, et al, J Biol. Chem., 267 (8):5712-21, 1992; Rando, R F et al., J Biol Chem, 270 (4):1754-60, 1995; Benimetskaya L, et al., Nucleic Acids Res., 25 (13):2648-56, 1997). In addition, ODNs containing an immune stimulatory CpG motif and 4 consecutive G nucleotides (class A ODNs) induce interferon-γ production and a Th1 shift in the immune response. Moreover, in preclinical disease models, Class A ODN have been shown to induce a TLR-mediated immune response.
In addition, oligonucleotides containing guanosine strings have been shown to form tetraplex structures, act as aptamers and inhibit thrombin activity (Bock L C et al., Nature, 355:564-6, 1992; Padmanabhan, K et al., J Biol. Chem., 268 (24):17651-4, 1993). Thus it is not clear whether single-stranded or multiple-stranded structures are effective at suppressing TLR9 activation.
Thus, there is a need for effective antagonist of TLRs without a concern that they will form secondary structures.